Objective: The present study aimed to compare body dissatisfaction, food choices, physical activity and weight-management practices by gender and school type. Design: A questionnaire was used to obtain height, weight, body image perception using Stunkard's figure rating scale, food choices, physical activity and weightmanagement practices. Setting: Nine single-and mixed-gender schools located in Bangkok Metropolitan Region, Thailand. Subjects: Students in 10th-12th grade, aged 15-18 years (n 2082). Results: Only 18 % of females and 21 % of males did not indicate body dissatisfaction. About 66 % of females selected a thinner ideal figure than their current figure. Among males, 44 % wanted a thinner figure, but 35 % wanted a bigger figure. However, univariate analysis found differences by school type but not gender in the degree of body dissatisfaction; students in single-gender schools had more body dissatisfaction. Females reported using more weight-management practices but less physical activity, while males reported healthier food choices. Participants in single-gender schools had healthier food choices compared with those in mixed-gender schools. Adolescents who were at increased risk of a greater degree of body dissatisfaction were females, attended single-gender schools, had lower household income, higher BMI and less physical activity. Conclusions: Most participants reported being dissatisfied with their current body shape, but the type and level of dissatisfaction and use of weight-management practices differed by gender and type of school. These findings suggest that programmes to combat body dissatisfaction should address different risk factors in males and females attending single-and mixed-gender schools.